Given :
The ball of a ballpoint pen is 0.5 mm in diameter and has an ASTM grain size of 12.
To Find :
How many grains are there in the ball?
Solution :
Volume of ball of the ballpoint is :

Now, grain size of 12 has about 520000 grains/mm³.
Therefore, number of grains are :

Oceanic crust is being formed it is because of the tectonic plates. Tectonic plates work because of volcanic eruption every time it will erupt the tectonic plates underground will have more pressure on magma, then below there will be a volcano thats why their is a volcano in ocean. The heat rises up then it will open, thats what we call divergent bounderies then their will be earthquakes form. Then another plate opens up and the crust is going down, it will stop if the volcano stops erupting because there is more lava left in volcano then it will go underwater and thats why oceanic crust is being formed.
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Answer:
D. Asthenosphere
Explanation:
The asthenosphere is relatively plastic part of the mantle which underlies the brittle lithosphere. In the asthenosphere, it is generally believed that the rocks are in ductile state and easily moves. It is the site of convection within the earth. In mantle convection, hot and light materials rises and keeps moving into upper crustal levels till they solidify. Here also, cold and denser materials sinks deeper till they turn to melt. This differences in temperature and density sets up a convective cell within the mantle. Several convective cells are in the mantle.
Answer:
m1u1+m2u2=(m1+m2)v.
500×4+1500×2=(500+1500)V.
2000+3000=2000V.
5000=2000V.
V=2.5m/s